/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 */
package org.apache.mina.core.service;

import org.apache.mina.core.session.IoSession;

/** Handles all I/O events fired by MINA. */
public interface IoHandler {
	/**
	 * Invoked from an I/O processor thread when a new connection has been created.
	 * Because this method is supposed to be called from the same thread that handles I/O of multiple sessions,
	 * please implement this method to perform tasks that consumes minimal amount of time
	 * such as socket parameter and user-defined session attribute initialization.
	 *
	 * @param session The session being created
	 * @throws Exception If we get an exception while processing the create event
	 */
	void sessionCreated(IoSession session) throws Exception;

	/**
	 * Invoked when a connection has been opened.  This method is invoked after {@link #sessionCreated(IoSession)}.
	 * The biggest difference from {@link #sessionCreated(IoSession)} is that it's invoked
	 * from other thread than an I/O processor thread once thread model is configured properly.
	 *
	 * @param session The session being opened
	 * @throws Exception If we get an exception while processing the open event
	 */
	void sessionOpened(IoSession session) throws Exception;

	/**
	 * Invoked when a message is received.
	 *
	 * @param session The session that is receiving a message
	 * @param message The received message
	 * @throws Exception If we get an exception while processing the received message
	 */
	void messageReceived(IoSession session, Object message) throws Exception;

	/**
	 * Handle the closure of an half-duplex TCP channel
	 *
	 * @param session The session which input is being closed
	 * @throws Exception If we get an exception while closing the input
	 */
	void inputClosed(IoSession session) throws Exception;

	/**
	 * Invoked when a connection is closed.
	 *
	 * @param session The session being closed
	 * @throws Exception If we get an exception while processing the close event
	 */
	void sessionClosed(IoSession session) throws Exception;

	/**
	 * Invoked when any exception is thrown by user {@link IoHandler} implementation or by MINA.
	 *
	 * @param session The session for which we have got an exception
	 * @param cause   The exception that has been caught
	 * @throws Exception If we get an exception while processing the caught exception
	 */
	void exceptionCaught(IoSession session, Throwable cause) throws Exception;
}
